Written by ALLAN HEINBERG Pencils & Cover by JIM CHEUNG 'SIDEKICKS' The Young Avengers declare war on one of the Avengers' most powerful and terrifying foes -- but first they must defeat his new allies: Captain America and Iron Man. It's the Young Avengers versus the old Avengers in a battle for the team's future -- and the kids' survival. Part 4 (of 6).